Truncation of the Appalachian Piedmont beneath the Coastal Plain of Alabama: Evidence from new magnetic data

A new aeromagnetic survey of a part of southern Alabama reveals that magnetic signatures of the Appalachian Piedmont are truncated by a major magnetic lineament beneath the Gulf Coastal Plain. Mylonitic rocks have been recovered from a drillhole along this lineament, which is probably a fault zone of late Paleozoic and/or Triassic-Jurassic age. We suggest that this fault zone may initially have been the Alleghanian convergent suture between the North American craton and accreted terranes to the southeast. The zone may have been locally reactivated as part of an extensive buried Triassic-Jurassic graben system.